This invention relates to an exhaust muffler for use on marine engines of the type found on inboard/outboard power boats, and specifically to an outboard exhaust muffler which is located outside the hull and aft of the transom.
Inboard/outboard type power boats typically have a plurality of exhaust pipes extending through the transom at the stern of the boat. These exhaust pipes are typically located slightly above the waterline. With larger marine engines, the exhaust noise emanating from the exhaust pipes can be substantial. Such exhaust noise is often disturbing to occupants of the power boat, to water skiers who are the following the boat, to other boaters and to nearby residents.
Many communities have established anti-noise ordinances which prohibit power boats producing levels of noise above certain decibel limits, particularly in connection with waterways that extend through residential communities. For these reasons and others, it is desirable to provide a muffler at the stern of the power boat to reduce the noise of engine exhaust.
Typical examples of prior art power boat mufflers intended for this purpose are shown in U.S. Pat. Nos. 4,744,778 and U.S. Pat. No. 4,786,265. These devices provide a combination swim platform and muffling device mounted at the stern of the boat. They generally include one or more vertical baffles extending down into the water that partially fills a muffling chamber. With this system, the pressure of the exhaust gases forces the gas below the water level and through to the other side of the baffle to another chamber from which the exhaust gas is discharged, usually through an exhaust outlet with an integral flapper valve.
The marine engine exhaust muffler of the present invention provides an improved construction over that described above and affords other features and advantages heretofore not obtainable.